Known hoses are generally manufactured in one of two ways. If the material employed is rubber or a synthetic rubber, the hose is generally made by extrusion or by being built-up on a rotating mandrel. In the latter case, the final step of the manufacturing process is a vulcanization stage. A hose produced from these materials may be fire-retardant but not fire-proof. A major disadvantage of such a hose is, however, the difficulty of incorporating other materials therein to vary the characteristics of the finished hose.
The problems associated with natural or synthetic rubber hoses, can, to some extent, be overcome by employing composite hoses. A composite hose, unlike a rubber hose, is built up in unvulcanised layers. Generally speaking, such a hose is produced by initially providing a wire helix which forms, effectively, a hollow internal former. Sheets of fabric and/or plastics material films are then successively wound onto the wire former. Amongst plastics materials which may be employed as the films are polypropylene, polyesters and polytetrafluoroethylene. A further helical wire is then wound around the outermost film or sheet of fabric. This outer wire helix binds the fabric layers and film layers together.
The wound layers of fabric and/or films give the composite hose thus produced greater flexibility than a hose made from natural or synthetic rubber. This is of particular advantage if the intended use of the hose is for loading and unloading petrol tankers and the like or for transferring fuels and oils between a ship and the shore. In addition to the additional flexibility, the advantages of a composite hose over a rubber hose are that it is lighter in weight, cheaper to manufacture and, depending upon the composition of the layers employed, it has a winder range of resistance to chemical corrosion. However, composite hoses have one major disadvantage compared with natural or synthetic rubber hoses. This is the extreme flammability of conventional composite hoses.